The present invention relates generally to bicycle derailleurs, and more particularly, is directed to flexible covers for bicycle derailleurs to protect the same from contaminants such as mud.
In order to provide different gear ratios during pedaling, a plurality of different sized chain sprockets are mounted for rotation along the axes of the rear hub and the pedal shaft of the bicycle. Typically, there are two or three different sized chain sprockets, known as chain rings, rotatable along the axis of the pedal shaft, and six or seven different sized chain sprockets, known as freewheel cogs, mounted in spaced relation on a free wheel and rotatable along the axis of the rear hub. The number of available gear ratios increases with the number of chain rings and cogs that are provided. The cogs (and chain rings) are spaced apart from each other, with the largest diameter ones to the inside (or outside) and the others decreasing in diameter toward the outside (or inside).
Because there are a plurality of different sized freewheel cogs associated with the rear wheel hub and a plurality of chain rings associated with the pedal shaft, it is necessary to move the chain from one freewheel cog to another and/or from one chain ring to another, to change gears. This operation is performed by a front derailleur associated with the chain rings and a rear derailleur associated with the free wheels, and particularly, with the chain at such positions.
A conventional front derailleur includes a clamping assembly which clamps the derailleur to the seat tube of the bicycle, a cage assembly which moves the chain from one chain ring to another, and a controller which connects the cage assembly to the clamping assembly and which, more importantly, controls movement of the cage assembly to control the latter to move the chain from one chain ring to another.
Specifically, the controller includes an upper pivot head fixed to the clamping assembly, and inner and outer spaced apart pivot bars, each pivotally connected at its upper end to the upper pivot head. The lower end of the inner pivot bar is pivotally connected with the inner cage plate of the cage assembly, and the lower end of the outer pivot bar is pivotally connected with a cross bar of the cage assembly. A return spring is provided around the lower pivot pin of the inner pivot bar to normally bias the cage assembly inwardly of the bicycle. Further, a pivot bar extension extends from the pivoted end of the inner or outer pivot bar, and a cable is secured thereto. The cable extends to a gear shift lever on the bicycle. When the cable is pulled, the pivot bars pivot outwardly against the force of the return spring so as to move the cage assembly outwardly in order to move the chain. The cable can be connected to the extension from below, in which case the derailleur is a bottom pull front derailleur and the pivot bar extension extends from the pivoted end of the outer pivot bar, or from above, in which case the derailleur is a top pull front derailleur and the pivot bar extension extends from the pivoted end of the inner pivot bar.
A conventional rear derailleur includes a clamping assembly which secures the rear derailleur to a rear drop-out or rear axle holder of the frame of the bicycle, a chain cage which moves the chain from one cog to another, and a controller which connects the chain cage to the clamping assembly and which, more importantly, actuates the chain cage to control the latter to move the chain from one cog to another.
Specifically, the clamping assembly includes a clamping head through which a bolt extends for securing the rear derailleur to a rear drop-out or rear axle holder of the frame.
The chain cage includes two parallel, spaced apart cage plates. The inner and outer cage plates are connected together at the proximal end by a pivot shaft having a jockey pulley rotatably mounted thereon between the cage plates, and are connected together at the distal end by a pivot shaft having an idler pulley rotatably mounted thereon between the cage plates.
The controller includes an upper pivot head having the clamping head formed as an integral extension thereof. Inner and outer spaced apart pivot bars are pivotally connected at their upper ends by pivot pins to the upper pivot head. The lower ends of the inner and outer pivot bars are pivotally connected by pivot pins to an inwardly extending lower pivot head, and a spring is provided about a lower pivot pin to normally bias the lower pivot head outwardly of the bicycle relative to upper pivot head. The lower pivot head is fixed to the proximal end of the outer cage plate.
Further, a pivot bar extension extends inwardly from a midpoint of the outer pivot bar, and a cable is secured thereto by a cable anchor bolt thereat. The cable extends upwardly through a guide bore as an extension of the upper pivot head, to a gear shift lever on the bicycle.
When the cable is pulled up, the pivot bars pivot inwardly against the force of the return spring so as to move the chain cage inwardly of the bicycle, thereby moving the chain from one cog to another.
However, a problem that occurs in many situations, and particularly when racing bicycles in muddy conditions, is that mud and other grit cake onto the controller of the front and/or rear derailleur. Another problem is in cold conditions where water freezes onto the controller. As a result, the moving parts of the controller may become inoperable or damaged, or at least, the performance may be severely degraded. The moving parts include the pivot bars, pivot or bearing assemblies which pivotally mount the pivot bars, and the return spring. Further, even if the controller is operable, it may wear faster, requiring more frequent replacement. This is because the mud and grit act like sandpaper and cut into the bearing surfaces, causing premature wear which translates into play or slop in the mechanism. Still further, because of such mud and other grit, it is necessary to constantly clean the derailleurs, which is time-consuming and burdensome.
Although various rear derailleur guards are known which are positioned to the outside of the outer cage plate to protect the cage plates of a rear derailleur from impact, such as disclosed in U.S. Pat. No. 3,184,993 to Swenson and U.S. Pat. No. 4,905,541 to Alan, these guards do nothing to prevent mud and other grit from clogging operation of the derailleur controller. Further, bicycle chain guards which protect the chain are known from U.S. Pat. No. 4,507,105 to Stottmann et al.
Although various boots are known for machinery parts, none of these boots are used for bicycle derailleurs and are therefore configured very differently. For example, see U.S. Pat. No. 4,276,786 to Langenstein with respect to earth moving vehicles and the like. See also U.S. Pat. No. 4,581,265 to Follette and U.S. Pat. No. 4,813,913 to Belter.